The translocator protein (TSPO), formerly known as the peripheral benzodiazepine receptor (PBR), is an 18 kDa protein mainly found on the outer mitochondrial membrane. It has been shown to be overexpressed in CNS diseases and in certain types of cancer and has become an attractive target in imaging agent development. Several small molecule PET and SPECT ligands has been developed for TSPO imaging of PBR, such as [11C]PK11195, Ro 5-4864, DAA1106, PBR28, AC-5216, Vinpocetine and [11C]DPA-713.
DPA-713 is a small molecule that binds to the translocator protein (TSPO), which is upregulated in activated′ leukocytes, some malignant tumors and tissues involved in steroid biogenesis.
DPA-713 is a compound from the family of pyrazolopyrimidines which is twice as potent as PK 11195 and 10 times more hydrophilic. Several radiolabeled PET and SPECT ligands has been developed, including [11C]DPA-713, [18F]DPA-714 and [125I]DPA-713. Imaging studies in animal models and humans have shown promising TSPO targeting characteristics.
Presently there still exists a need for non-radioactive imaging agents which are specific for the TSPO enzyme, for diagnosis and treatment of diseases.